Hi Donna,
To delete an attachment, simply click the Edit record and choose to
delete, here is a movie to show you how:
http://screencast.com/t/YTBiYzJlMDgt.
Regarding issues with File Not Found, I have not seen that issue. If
you encounter it again, please fill out a support ticket at
http://www.softwareplanner.com/support and let them know what project
you are logged into, what area you are attaching files to
(requirements, etc), what record you are attaching it to and the
file. Then they can try to help you debug that.
Thanks!
Steve